The objective of the current research is to answer the following question: Does membrane transport in the nervous system change with age? Specifically, (1) are there changes in membrane transport mechanisms by which the cell obtains from the extracellular fluid metabolic substrates for energy metabolism and protein synthesis? and (2) are there changes in membrane transport processes necessary for normal transmitter function? The specific aims are as follows: (1) To measure the initial rates of uptake of 2-deoxy-D-glucose, L-glutamic acid, choline, n-epinephrine, and GABA in a synaptosomal preparation from rat brain cortex as a function of age, and from these initial rates, calculate the apparent Michaelis constant (Kt) and maximum rate of uptake (Vm). (2) To repeat (1) for n-epi only in synaptosomes from hypothalamus. (3) To determine whether the degree of Na-dependence of uptake changes with age, and whether the effect of Na on the kinetic constants changes with age. (4) To determine whether there is any change in energy-dependence with age. This can be ascertained by studies of uptake in the presence and absence of metabolic inhibitors and by studies utilizing lowered temperatures.